Half-tone screen determiner



July 10, 1951 A. H. GAEBEL HALF-TONE SCREEN DETERMINER Filed Dec. 28,1949 INVENTOR. IJrZ/zur 1. G'ae Bel Patented July 10, 1 951 UNITEDSTATES ram OFFICE HALF-TONE. SCREEN DETERMINER Arthur Henry Gaebel,Larchmont, N. Y.

Application December 28, 1949, Serial No. 135,356

This invention relates to a device for counting the number of lines perlinear inch of half tone screens used in the printing art.

The principal object of the present invention is the provision of adevice of the indicated character having a comparatively greatercounting range than analogous devices hitherto available.

A further object of the invention is the provision of a device of theindicated character which is accurate, and visually indicates in a clearmanner the exact count of the lines or rulings of half-tone screens.

3 Claims. (Cl. 8814) The present invention also resides in theconvenience and the economy derived therefrom.

The nature of the invention and its distinguishing features andadvantages will appear when the following specification is read inconjunction with the accompanying drawing, in which:

Fig. 1 is a top plan view of a device constructed in accordance with thepresent invention, portions thereof being broken away to show certainfeatures.

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a fragmentary enlarged sectional view taken on the line 3-3 ofFig. 1;

Fig. 4 is a plan view illustrating the manner in which a half-tonescreen or a half-tone print affects the present device when laid thereonfor the purpose of counting the lines or rulings per linear inch.

Fig. 5 shows portions of some of the radial interference lines and therelation of the lines greatly magnified.

Referring now more particularly to the several views of the drawing, itwill be apparent that the device consists of a flat rectangular plateID, the plate being substantially square in the present instance,although the plate may be any other suitable shape.

The plate l comprises two transparent laminations II and 12. Thelaminations in the present instances are made of Vinylite, but may bemade of any other suitable material. The lamination H has appliedthereto a layer of opaque substance 13, surrounding a portion whichremains clear or transparent thereby providing a window Hi. Thelamination II also has printed thereon in the clear portion 14 a groupof opaque radial lines l having a common point of radiation. The linesl5 are spaced equidistantly. The center line C of the group is disposedat an angle of forty-five degrees with respect to any one of thestraight edges of the plate iii. There are about one hundred lines E5 inthe present instance. In Fig. 4 some of the lines are omitted for thesake of convenience.

Each line i5 is tapered. It tapers toward the common point of radiation.The clear spaces between the lines I5 are equal in shape and length tothe lines I5, or in other words, the spaces taper similarly to thetapering of the lines l5, as shown in Fig. 5.

The opaque layer 43 on the lamination II has imprinted thereon anumerical scale I6 bordering the window M at each side thereof. Eachscale i5 is subdivided according to the number of lines or rulings of ahalf-tone screen per linear inch, which lines are designated by thescale numerals H ranging from 55 to 150.

Half-tone screens through which almost all magazine and newspaperillustrations are produced are engraved in standard number of lines perlinear inch in both directions at ninety degree angles. Such screens aremade of sheet glass having thereon opaque lines, and the lines are equalin width to the transparent spaces between them. The lines or rulings ofthe screens used are 50, 60, 65, 70, '75, 80, 85, 100, 110, 120, 133,150 etc. per linear inch.

In the present device according to the mentioned screens, the grid orgroup of lines I5 may be or less to 150 or more per linear inch. At 50lines and transparent spaces, the width of each line is of an inch as isthe clear space between two lines. At 150 lines, the width of each lineas well as the clear intervening space is of an inch.

The present device having the features hereinabove described when laidfiatwise on a screen or half-tone print with the center line C at 45degrees will produce a definite pattern or moire in the form of a fourpointed star S, by reason of the interference of the lines and the linesof a screen or dots of a half-tone, as the case may be. As shown in Fig.4 two points diametrically opposite each other of the star point to theindices lid of the scales l6, thereby visually indicating that thescreen has lines per linear inch, or in the case of a half-tone printthe same count would be indicated.

By making the lines 55 and the intervening spaces tapered, it ispossible to obtain a more pronounced and definitive star patterncorrectly determining the number of rows of dots per linear inch in half-tone screens.

It is to be understood that the invention is not restricted to theembodiment illustrated and described, but includes all changes andmodifications coming within the scope of the appended claims.

I claim:

1. A half-tone screen determiner consisting of a flat plate having astright edge, said plate having a transparent portion, and an opaqueportion surrounding said transparent portion, and there being located onsaid plate in said transparent portion a group of tapered radial opaquelines tapering toward a common point of radiation and spacedequi-distantly, the center line of said group being disposed at an angleof forty-five degrees with respect to said straight edge; and said platehaving a numerical scale thereon bordering said transparent portion,cooperating with said lines when the plate is laid flatwise on ahalftone and said scale then indicating the number of lines per linearinch of the screen.

2. A half-tone screen determiner as set forth in claim 1, wherein thespaces between the lines are tapered similarly to the tapering of thelines.

3. A half-tone screen determiner consisting of a flat plate composed oflaminations bonded together fiatwise, there being two transparentlaminations, one of said laminations having a layer of opaque substancethereon providing the plate with a clear portion, one of saidlaminations having located thereon at said clear portion a group oftapered radial opaque lines tapering toward a common point of radiationand spaced equi-distantly, the center line of said group being disposedat an angle of forty five degrees with respect to at least one edge ofthe plate, and said opaque layer having a numerical scale thereonbordering said clear portion cooperating with said lines when the plateis laid flatwise on a halftone screen, and said scale then indicatingthe number of lines per linear inch of the screen.

ARTHUR HENRY GAEBEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,831,536 Luhn Nov. 10, 19312,125,887 Cook Aug. 9, 1938 2,446,047 Kent July 27, 1948 2,475,490Gelardin July 5, 1949

